/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.linkis.engineconnplugin.flink.client.sql.operation.impl;

import org.apache.linkis.engineconnplugin.flink.client.context.ExecutionContext;
import org.apache.linkis.engineconnplugin.flink.client.sql.operation.NonJobOperation;
import org.apache.linkis.engineconnplugin.flink.client.sql.operation.result.ColumnInfo;
import org.apache.linkis.engineconnplugin.flink.client.sql.operation.result.ConstantNames;
import org.apache.linkis.engineconnplugin.flink.client.sql.operation.result.ResultKind;
import org.apache.linkis.engineconnplugin.flink.client.sql.operation.result.ResultSet;
import org.apache.linkis.engineconnplugin.flink.context.FlinkEngineConnContext;
import org.apache.linkis.engineconnplugin.flink.exception.SqlExecutionException;

import org.apache.flink.table.api.Table;
import org.apache.flink.table.api.TableEnvironment;
import org.apache.flink.table.types.logical.VarCharType;
import org.apache.flink.types.Row;

/** Operation for EXPLAIN command. */
public class ExplainOperation implements NonJobOperation {
    private final ExecutionContext context;
    private final String statement;

    public ExplainOperation(FlinkEngineConnContext context, String statement) {
        this.context = context.getExecutionContext();
        this.statement = statement;
    }

    @Override
    public ResultSet execute() throws SqlExecutionException {
        final TableEnvironment tableEnv = context.getTableEnvironment();
        // translate
        try {
            final Table table = createTable(context, tableEnv, statement);
            String explanation = context.wrapClassLoader(() -> tableEnv.explain(table));
            return ResultSet.builder()
                    .resultKind(ResultKind.SUCCESS_WITH_CONTENT)
                    .columns(
                            ColumnInfo.create(
                                    ConstantNames.EXPLAIN_RESULT,
                                    new VarCharType(false, explanation.length())))
                    .data(Row.of(explanation))
                    .build();
        } catch (SqlExecutionException t) {
            throw t;
        } catch (Exception t) {
            // catch everything such that the query does not crash the executor
            throw new SqlExecutionException("Invalid SQL statement.", t);
        }
    }

    /** Creates a table using the given query in the given table environment. */
    private Table createTable(
            ExecutionContext context, TableEnvironment tableEnv, String selectQuery)
            throws SqlExecutionException {
        // parse and validate query
        try {
            return context.wrapClassLoader(() -> tableEnv.sqlQuery(selectQuery));
        } catch (Exception t) {
            // catch everything such that the query does not crash the executor
            throw new SqlExecutionException("Invalid SQL statement.", t);
        }
    }
}
